package com.custom.executor;

import com.custom.config.BoundSql;
import com.custom.pojo.Configuration;
import com.custom.pojo.MappedStatement;
import com.custom.utils.GenericTokenParser;
import com.custom.utils.ParameterMapping;
import com.custom.utils.ParameterMappingTokenHandler;

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor
{
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InvocationTargetException, IntrospectionException, InstantiationException {

        PreparedStatement preparedStatement=getPreparedStatement(configuration,mappedStatement,params);
        //5. 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        // 6. 封装返回结果集
        while (resultSet.next()){
            Object o =resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {

                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段的值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);


            }
            objects.add(o);

        }
        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InvocationTargetException, IntrospectionException, InstantiationException {
        PreparedStatement preparedStatement=getPreparedStatement(configuration,mappedStatement,params);
        return preparedStatement.executeUpdate();
    }

    /**
     * 获取预处理的对象并设置参数
     * @param configuration
     * @param mappedStatement
     * @param params
     * @return
     * @throws SQLException
     */
    private PreparedStatement getPreparedStatement(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        //1.注册驱动,获取连接
        Connection connection=configuration.getDataSource().getConnection();

        //2.获取sql语句
        String sql=mappedStatement.getSql();
        BoundSql boundSql=getBoundSql(sql);

        //3.获取预处理对象:preparedStatement
        PreparedStatement preparedStatement=connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
        String paramterType=mappedStatement.getParameterType();
        Class<?> paramtertypeClass=getClassType(paramterType);
        if(paramtertypeClass==Integer.class){
            preparedStatement.setObject(1,params[0]);
        }else {
            List<ParameterMapping> parameterMappingList=boundSql.getParameterMappingList();
            for (int i = 0; i < parameterMappingList.size(); i++) {
                ParameterMapping parameterMapping = parameterMappingList.get(i);
                String content = parameterMapping.getContent();
                //反射
                Field declaredField = paramtertypeClass.getDeclaredField(content);
                //暴力访问
                declaredField.setAccessible(true);
                Object o = declaredField.get(params[0]);
                preparedStatement.setObject(i+1,o);

            }
        }

        return preparedStatement;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType!=null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;

    }
    /**
     * 完成对#{}的解析工作,1.将#{}使用？进行代替,2.解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql){
      //标记处理类:配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler=new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser=new GenericTokenParser("#{","}",parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql=genericTokenParser.parse(sql);
        List<ParameterMapping> parameterMappings=parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql=new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }
}
